Hi Abigail,
It’s unlikely that this guy you met on a dating app repeatedly told you that you are out of his league so as to let you down easy, being that you were yet to meet him in person.
It is also unlikely that he was being manipulative, as this would be very presumptuous of him so early on in his interaction with you.
If anything, he said those words in an attempt to prepare you for a disappointment if you were both to meet on a date and you were left disappointed with what you saw.
He seems to be someone with low self-esteem. If you noticed that his body language was closed off during the date, there is a good chance that he is just not particularly confident.
Closed off body language would be when he is avoiding sustained eye contact with you, is keeping you at a distance physically and is often distracted by something or someone else throughout the date.